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ILLINOIS  BIOLOGICAL 
MONOGRAPHS 


Vol.  II  October,  1915  No.  2 


Editorial  Committee 


Stephen  Alfred  Forbes  William  Tri lease 

Henry  Baldwin  Ward 


Published  under  the 

Auspices  of  the  Graduate  School  by 

THE  University  of  Illinois 


Copyright,  1915 
By  the  University  of  Illinois 

Distributed   February    25,    1916 


ON  THE 

OSTEOLOGY  OF  SOME  OF 

THE  LORICATI 


WITH  FIVE  PLATES 


JOHN  EARL  GUTBERLET 


Contributions  from  the 

Zoological  Laboratory  of  the  University  of  Illinois  under   the   direction   of 

Henry  B.  Ward.  No.  56 


TABLE  OF  CONTENTS 


PAGE 

Introduction  5 

Ophidon  elongatus 

The  Cranium.' 5 

Facial    Bones 16 

Scorpionichthys  marmoratus 

The  Skull 21 

Facial   Bones 23 

Hexagrammos  decagranimus 

The  Skull 25 

Facial   Bones ^ 26 

Summary 27 

Bibliography 29 

Explanation  of   Plates 30 

Plates  31 


175]  OSTEOLOGY    OF    LORICATI  —  GUTBERLET 


INTRODUCTION 

The  suborder  Loricati  is  characterized  by  the  extension  of  the 
third  suborbital  bone  across  the  cheek  to  the  preopercle.  This  group 
has  a  wide  range  of  variation  and  Gill  has  divided  it  into  several  families 
of  which  the  rock  fishes,  or  Scorpaenidae,  are  more  generalized  and  the 
sculpins,  or  Cottidae,  are  the  most  specialized.  The  family  Hexagrammi- 
dae  comes  between  the  two  extremes,  being  more  nearly  related  to  the 
Scorpaenidae  than  to  the  Cottidae. 

The  purpose  of  this  paper  is  to  make  a  comparative  study  of  the 
osteology  of  these  forms  in  order  to  determine  their  relationship.  Allen 
(1905)  states  that  there  are  many  points  of  resemblance  to  the  Cot- 
tidae to  be  found  in  their  osteology,  visceral  organs,  and  vascular 
systems,  and  that  Ophidon  is  about  as  closely  related  to  Scorpionichthys, 
a  sculpin,  as  it  is  to  Hexagrammos,  and  should  be  regarded  as  a  type  of  a 
distinct  family.  For  this  study  Ophidon  elongatus  and  Hexagrammos 
decagrammus  of  the  Hexagrammidae  and  Scorpionichthys  marmoratus 
of  the  Cottidae  were  selected.  The  material  was  collected  at  Monterey 
Bay,  California,  by  Mr.  William  F.  Allen  under  whose  direction  the 
work  was  carried  on  at  the  Zoological  Laboratory  of  the  University  of 
Illinois. 


OPHIDON  ELONGATUS 
The  Cranium 

Except  for  a  few  ridges  and  grooves,  the  entire  dorsal  surface  of 
the  skull  (Fig.  1)  is  flattened.  On  the  anterior  half  there  is  a  median 
rectangular  groove  which  extends  from  between  the  posterior  boundaries 
of  the  orbits  to  the  median  ridge  of  the  ethmoid.  Posterior  to  the  groove 
the  parietals  form  a  ridge  on  either  side,  extending  laterally  and  poster- 
iorly, from  the  median  line  to  the  lateral  edges  of  the  epiotics.  These 
ridges  are  continuations  of  the  long  rounded  ridges  of  tlio  frontals  which 
form  the  sides  of  the  rectangular  grooves.  The  surface  of  the  frontals, 
posterior  to  the  orbits,  is  somewhat  porous  and  lias  striatious  which  pass 
caudad  and  mesad  from  the  edge  of  the  orbits  toward  the  parietals 

The  temporal  fossa  is  formed  by  the  pterotics,  frontals,  parietals 
and  epiotics.     It  extends  caudad  from  the  latero-posterior  edge  of  the 


6  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [176 

frontal  to  the  caudad  end  of  the  skiill.  In  the  anterior  half  it  is  compar- 
atively shallow,  but  throughout  the  posterior  half  it  has  a  depth  of 
nearly  one-third  that  of  the  skull.  The  fossa  harbors  some  of  the 
muscles  of  the  shoulder  girdle.  The  dilatator  fossae  (Fig.  5-6)  are 
pits  on  the  dorso-lateral  edges  of  the  skull,  directly  above  the  two  articu- 
lar facets  of  the  hyomandibular.  Anteriorly,  each  pit  lies  in  the 
sphenotic  and  posteriorly  in  the  pterotic.  The  pterotic  forms  the  greater 
part  of  the  roof  of  the  pit  while  the  most  dorsal  edge  of  the  prootic  forms 
a  part  of  the  ventral  edge.  Two  foramina  are  present  in  the  pit  for  the 
branches  of  the  oticus  vessels.  The  arch  of  the  prootic  Avhich  forms 
the  bridge  over  the  foramina  for  the  fifth  and  seventh  nerves,  the 
juglar  vein  and  the  external  carotids  is  conspicuous  in  Opkidon.  It 
begins  at  the  anterior  central  portion  of  the  bone  and  extends  dorsad  to 
the  ventral  edge  of  the  anterior  articular  facet  of  the  hyomandibular 
on  the  sphenotic. 

Vomer. — The  vomer  (Fig.  1)  is  the  anterior  bone  of  the  skull 
and  caps  the  cartilage  from  the  ends  of  the  ethmoid  and  the  prefrontals. 
It  possesses  both  dorsal  and  ventral  processes.  The  dorsal  and  anterior 
one  passes  upward  and  posteriorly  and  articulates  with  the  ethmoid  and 
prefrontals.  The  ventral  process  forms  a  part  of  the  ventral  surface; 
it  passes  posteriorly  and  gradually  tapers  to  a  point  in  the  parasphenoid. 
A  V-shaped  slit  is  present  in  the  dorsal  process  and  forms  a  trough-like 
cavity  ^^^th  the  ventral  process,  alloAving  the  cartilaginous  portion  of 
the  ethmoid  to  pass  into  it.  The  anterior  edge  is  broad  V-shaped  in 
the  median  line  and  rounded  from  the  median  portion  laterad  forming  a 
large  expansion  at  each  side.  Two  kinds  of  teeth  are  present  on  the 
vomer;  an  inner  row  of  large  canine-shaped  ones  and  ail  outer  row  of 
the  villiform  variety  in  which  the  teeth  are  irregularly  arranged.  Both 
kinds  are  slightly  curved  caudad  and  are  placed  in  sockets.  The 
maxilla  and  premaxillary  both  articulate  just  above  the  vomer  and  cover 
it  entirely. 

Ethmoid. — The  anterior  dorsal  portion  of  the  ethmoid  (Fig.  1, 
6,  eth)  is  strongly  keeled,  while  the  posterior  portion  is  concave  longi- 
tudinally and  ends  between  the  frontals  where  it  tapers  to  a  point. 
There  is  a  narrow  median  ridge  on  the  keeled  portion  extending  its  full 
length  Avith  a  V-shaped  slit  in  the  anterior  end.  The  ventro-lateral 
depression  of  the  anterior  portion  forms  a  cavity  between  it  and  the 
prefrontal,  these  parts  forming  the  ventral  and  mesial  osseous  walls 
of  the  nasal  pit.  The  longitudinal  groove  in  the  concave  portion  is 
formed  by  a  dorso-lateral  expansion  on  either  side  at  its  anterior  end. 
From  this  point  the  groove  passes  caudad  and  continues  as  the  rectangu- 
lar groove  between  the  ridges  of  the  frontals.  The  sides  of  the  posterior 
portion  are  eoneave  from  the  point  at  which  the  lateral  expansions  ex- 


177]  OSTEOLOGY  OF  LORICATI—GUTBERLET  7 

tend  out  from  the  median  line.  On  each  side  of  the  lateral  concave  sur- 
faces there  is  a  deep  pit  produced  by  several  pores. 

Prefrontal. — The  paired  prefrontals  or  ectethmoids  Fig.  1, 
6,  pfr)  are  lateral  to  the  ethmoid  and  anterior  to  the  frontals.  Each 
is  a  lateral  expansion  from  the  ethmoid  and  the  frontals,  having  a  broad 
base-like  portion  and  a  wing-like  process  extending  from  it  which  forms 
the  anterior  boundary  of  the  orbit.  The  anterior  portion  is  somewhat 
lower  than  the  rest  and  appears  as  a  shelf  at  the  side  of  the  ethmoid 
because  of  a  depression  on  its  anterior  dorsal  surface.  This  depression, 
together  with  a  similar  depression  on  the  latero-ventral  surface  of  the 
ethmoid  forms  a  part  of  the  bony  wall  of  the  nasal  pit.  The  wing-like 
process  is  narrow  antero-posteriorly  but  broad  and  flattened  dorso- 
ventrally.  The  end  is  rounded  and  forms  a  facet  for  articulation  with 
the  palatal  and  the  first  exorbital  bone.  A  small  ventral  process  on  the 
wing  meets  a  process  from  the  palatine.  From  the  base  of  the  wing- 
like portion  the  bone  flattens  out  antero-posteriorly  as  it  extends  ventro- 
mesad  to  its  articulation  with  the  parasphenoid.  There  is  a  foramen 
through  the  wing  near  its  suture  with  the  ethmoid  through  which  the 
olfactory  nerve  and  the  orbito-nasal  vein  and  artery  to  the  nasal  pit 
pass.  Above  the  point  where  the  prefrontal  unites  with  the  parasphe- 
noid they  come  in  contact  with  each  other  in  the  median  line  holding 
between  them  the  ventral  edge  of  the  cartilaginous  orbito-sphenoid 
which  extends  dorsad  and  caudad  forming  a  partial  partition  between 
the  orbits. 

Frontal. — The  paired  frontals  (Figs.  1,  6,  fr)  form  the  greater 
part  of  the  dorsal  surface  of  the  cranium.  At  the  anterior  end  of  each 
there  is  a  small  groove  produced  by  pores  in  the  bone.  The  lateral 
edges  of  the  posterior  portion  form  the  mesial  boundaries  of  the  orbits. 
The  posterior  portion  broadens  and  forms  the  posterior  and  dorsal 
boundaries  of  the  orbits.  At  this  point  the  frontals  are  slightly  rounded 
dorsad  and  the  bone  is  somewhat  porous,  possessing  several  striations 
which  start  at  the  posterior  boundary  of  the  orbit  and  radiate  caudad 
and  mesad  toward  the  median  line  to  the  parietal  bones.  The  lateral 
edges  of  the  posterior  portion  form  the  mesial  border  of  the  anterior 
part  of  the  temporal  fossa.  At  the  lateral  edge  on  the  posterior  border 
of  the  orbit  the  frontal  unites  with  the  sphenotic.  Its  lateral  edge  rests 
on  the  prefrontal  and  the  mesial  edge  rests  on  the  ethmoid.  In  the 
median  line  on  the  ventral  surface  there  is  a  cartilaginous  orbito- 
sphenoid  bone,  extending  to  the  parasphenoid  and  forming  a  partial 
partition  between  the  orbits.  The  ventral  surface  of  the  roof  of  the 
orbit  is  filled  with  large  pores  and  two  deep  grooves  which  become 
deeper  as  they  pass  caudad  into  the  deeper  part  of  the  frontal.  The 
mesial  edge  of  the  inner  groove  forms  a  large  flange  which  projects 


8  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [178 

ventrad  along  the  lateral  edge  of  the  brain  ease.  The  outer  edge  of  this 
flange  narrows  do^vn  and,  as  it  passes  ventrad,  it  is  drawn  out  to  a  thin 
process;  this  flange  and  the  thin  process  clsisp  the  small  alisphenoid 
between  them  as  in  Scorpaena  described  by  Allis.  The  ventral  surface 
of  the  posterior  portion  is  smooth  and  in  connection  with  supra-occipital 
which  forms  a  plate  beneath  the  parietals  and  posterior  part  of  the 
frontals  forms  the  roof  of  the  brain  case. 

Post  frontal. — The  postfrontal  (Fig.  1,  pfo)  is  a  small  tube- 
like bone  similar  to  the  one  described  by  Allis  in  Scorpaena  scorpus 
except  that  it  is  without  spines.  It  lies  on  the  part  of  the  dorsal  surface 
of  the  sphenotic  which  is  not  covered  by  the  frontal  and  pterotic.  The 
tube  extends  from  the  lateral  edge  of  the  sphenotic  caudo-mesad  to  the 
anterior  end  of  the  temporal  fossa. 

Sphenotic. — The  sphenotics  (Figs.  1,  6,  spo)  are  located  at  the 
lateral  margins  of  the  cranium,  just  posterior  to  the  orbits  and,  in 
conjunction  with  the  lateral  expansions  of  the  frontals  they  form  the 
posterior  boundary  of  the  orbit.  The  dorsal  surface  of  each  is  nearly 
flat,  except  for  a  groove  formed  for  the  postfrontal  bone  which  lies  within 
it.  It  thus  forms  supports  for  the  frontal,  the  postfrontal,  and  the  ptero- 
tic. It  forms  the  anterior,  lateral,  and  ventral  portions  of  the  cranium. 
The  anterior  margin  borders  on  the  orbit  and  the  ventro-lateral  edge 
forms  a  facet  for  the  articulation  with  the  anterior  head  of  the  hyomand- 
ibular.  Directly  dorso-anterior  to  the  facet  is  a  roughened  surface  which 
serves  for  the  attachment  of  one  of  the  palatal  muscles.  Dorso-posterior 
to  the  facet  is  a  depression,  the  dilatator  fossa,  the  posterior  part  of  the 
sphenotic  forming  the  anterior  part  of  the  depression.  Between  the 
dorsal  part  of  the  sphenotic  and  the  frontal,  beneath  the  postfrontal, 
there  is  a  small  foramen  which  transmits  one  of  the  branches  of  the 
otic  vessels.  The  sphenotic  also  forms  a  part  of  the  internal  brain 
case;  the  internal  surface  is  smooth  and  has  two  depressions,  separated 
by  a  thin  partition  of  bone  which  extends  mesad  into  the  brain  cavity. 

Prootic. — The  prootic  (Fig.  6,  pro)  forms  a  large  part  of  the 
lateral  surface  of  the  cranium.  It  is  bounded  dorsally  by  the  sphenotic 
and  pterotic,  anteriorly  by  the  alisphenoid  and  the  dorso-lateral  process 
of  the  parasphenoid,  ventrally  by  the  parasphenoid,  and  posteriorly 
by  the  basi-occipital  and  exoccipital.  MesiaUy  it  articulates  with  the 
basisphenoid  and  the  prootic  of  the  opposite  side.  On  the  ventral  sur- 
face it  is  overlapped  by  the  lateral  edges  of  the  posterior  portion  of  the 
parasphenoid.  The  prootics  form  the  lateral  walls  of  the  brain  case 
and  also  the  roof  and  walls  of  the  myodome.  The  brain  cavity  and  the 
myodome  are  separated  by  a  mesial  longitudinal  partition-like  process 
which  unites  with  a  similar  one  from  the  opposite  side  in  the  median 
line.    This  partition  begins  at  the  basioccipital,  which  also  forms  the 


179]  OSTEOLOGY   OF  LORICATI—GUTBERLET  9 

posterior  part  of  the  floor  of  the  brain  ease,  and  extends  dorso-cephalad 
until  it  reaches  the  processes  which  support  the  T-shaped  basisphenoid, 
leaving  a  small  wedge-shaped  slit  between  the  basisphenoid  and  the 
partition  for  the  opening  of  the  pituitary  body  from  the  brain  case. 
Near  the  lateral  wall,  just  posterior  to  the  process  which  supports  the 
basisphenoid,  a  small  foramen  for  the  sixth  nerve  preforates  the  parti- 
tion. Between  the  prootic,  alisphenoid,  and  the  dorso-lateral  process 
of  the  parasphenoid  there  is  a  large  foramen  through  which  the  anterior 
cerebral  vein,  the  ciliary  nerve,  and  ciliary  artery  pass.  On  the  front 
edge  of  the  foramen  and  slightly  mesad,  at  the  base  of  the  process  sup- 
porting the  basisphenoid,  there  is  a  second  small  foramen  for  the  third 
nerve.  On  the  lateral  surface  of  the  prootic  is  the  prootic  arcade,  which 
is  located  slightly  dorso-posterior  to  the  foramen  between  the  bones  just 
described  and  directly  ventral  to  the  anterior  articular  facet  for  the 
hyomandibular  on  the  sphenotic.  This  arcade  partly  shelters  two  fora- 
mina. The  anterior  and  larger  one  is  for  the  passage  of  the  jugular 
vein,  the  external  carotid  artery,  the  fifth  and  part  of  the  seventh  nerves. 
The  posterior  one  is  for  the  hyomandibular  part  of  the  seventh  nerve. 
There  is  another  small  foramen  for  the  fourth  nerve  just  anterior  to  the 
arcade.  The  arcade  forms  an  arch  through  which  the  jugular  vein  and 
external  carotid  artery  pass  after  they  have  passed  through  the  fora- 
men. On  the  inner  surface  the  brain  case  is  smooth  with  a  large  broad 
ridge,  produced  by  the  broad  groove  on  the  external  surface,  extending 
from  near  the  middle  just  behind  the  arcade  to  the  posterior  end  of  the 
bone  (where  it  unites  by  suture  with  the  exoccipital  and  the  ventral 
most  edge  of  the  pterotic)  and  continuing  caudad  as  the  ridge  on  the 
exoccipital.  Directly  ventral  to  the  ridge  on  the  internal  surface,  there 
is  a  deep  depression  or  groove  parallel  to  the  ridge  and  extending  the 
length  of  it  bordering  on  the  floor  of  the  brain  case.  This  groove  con- 
tinues caudad  into  the  basioccipital  where  it  finally  forms  a  recess  with 
the  overhanging  edge  of  the  exoccipital.  Directly  beneath  the  arcade 
there  is  a  flange-like  process  extending  from  the  floor  of  the  brain  case 
to  the  dorsal  edge  of  the  bone  where  it  unites  with  a  similar  process  of 
the  sphenotic.  This  flange-like  process  forms  two  recesses  for  parts  of 
the  anterior  semicircular  canal. 

Alisphenoid. — The  alisphenoids  (Fig.  6,  als)  are  small,  irregu- 
lar bones,  ventral  to  the  articulation  of  the  sphenotic  and  frontal  where 
they  are  held  in  place  by  the  clasp  of  the  ventral  flange  and  slender 
ventro-mesal  process  of  the  frontal.  Each  also  comes  in  contact,  ventrad 
and  caudad,  with  the  parasphenoid  and  prootic.  The  outer  surface  is 
porous  while  the  inner  surface  is  smooth  and  forms  the  latero-anterior 
part  of  the  brain  case.  A  large  foramen,  postero-ventral  to  the  alisphe- 
noid, and  between  it  and  the  prootic  and  the  dorso-lateral  process  of 


10  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [180 

the  parasphenoid,  allows  the  passage  of  the  anterior  cerebral  vein,  the 
ciliary  artery,  and  the  ciliary  nerve.  Allis  ( '09)  found  a  small  foramen 
for  the  anterior  cerebral  vein  perforating  the  alisphenoid  in  Scomber, 
Coitus,  Trigla,  Peristedion,  Dactylopterus,  and  Scorpaena  and  states 
that  Allen  (1905)  did  not  describe  it  in  Ophidon.  I  do  not  find  a 
foramen  perforating  the  alisphenoid  in  Ophddon  nor  in  ScOrpionichthys. 
The  anterior  cerebral  vein,  according  to  Allen  (1905),  passes  through 
the  foramen  formed  by  the  prootic,  the  dorso-lateral  process  of  the 
parasphenoid,  and  the  posterior  edge  of  the  alisphenoid. 

Parasphenoid. — The  parasphenoid  (Fig.  6,  ps)  is  the  longest 
bone  of  the  skull  and  forms  the  ventral  surface  of  the  entire  length  of 
the  cranium  with  the  exception  of  the  process  of  the  vomer  which  passes 
caudad  into  the  parasphenoid.  The  anterior  portion  is  almost  perfectly 
straight  on  the  ventral  surface  while  the  posterior  portion  is  slightly 
curved  upward  and  the  edges  of  the  bone  turn  up  dorso-lateraUy,  the 
entire  length  of  the  bone.  In  the  middle  portion  the  edge  projects 
upward  as  a  long  process  which  extends  dorso-laterally  to  the  edge  of 
the  alisphenoid.  Directly  posterior  to  the  process,  in  the  angle  between 
it  and  the  prootic,  is  a  foramen  through  for  the  internal  carotid  artery. 
The  bone  has  a  cqncave  longitudinal  groove  the  entire  length  of  the 
dorsal  surface  which,  in  the  anterior  portion,  is  divided  by  a  tall  parti- 
tion, extending  from  a  point  immediately  anterior  to  the  tall  processes 
to  the  anterior  end  of  the  bone  where  it  terminates  in  the  ethmoid  and 
the  vomer.  At  the  anterior  end  there  is  a  V-shaped  slit  on  the  ventral 
edge  for  the  postero-ventral  process  of  the  vomer.  The  posterior  end 
also  has  a  V-shaped  slit  extending  cephalad,  forming  the  posterior 
opening  of  the  myodome.  The  dorsal  surface  of  the  posterior  portion 
forms  a  part  of  the  floor  of  the  myodome,  between  the  prootics  and  the 
two  taU  dorso-lateral  processes  of  the  bone  itself.  This  portion  also 
forms  a  support  for  the  prootics  and  the  basioccipital. 

Basisphenoid. — The  basisphenoid  (Fig.  6,  hs)  is  a  T-shaped 
bone  forming  the  anterior  part  of  the  roof  of  the  myodome,  being  at- 
tached to  the  processes  extending  mesad  from  the  prootic,  just  postero- 
ventrad  to  the  alisphenoid.  The  pedicle  is  curved  ventro-cephalad  to 
the  parasphenoid  where  it  is  united  to  it  by  a  bulb  of  cartilage.  It  is 
laterally  flattened  and  the  rest  of  the  bone  between  the  prootic  processes 
is  dorsally  flattened  but  rounded  ventrally  and  slightly  curved  cephalad 
at  the  point  where  the  pedicle  process  projects. 

Pterotic. — The  pterotics  (Figs.  1,  6,  pto)  form  the  lateral  edges 
of  the  dorsal  surface  of  the  skull,  posterior  to  the  sphenotics  and  the 
postfrontals,  and  also  the  lateral  borders  of  the  temporal  fossa.  On  the 
dorsal  edge  of  such  there  is  a  narrow  ridge  extending  from  the  anterior 
end  to  beyond  the  middle  from  which  the  surface  gradually  slopes  to 


181]  OSTEOLOGY  OF  LORICATI—GUTBERLET  11 

the  lateral  edge  of  the  sknll.  A  foramen  for  a  lateral  line  canal  oceors 
at  the  posterior  end ;  the  whole  surface  being  nune  or  lew  performted. 
The  lateral  surface  of  the  pterotic  is  bounded  eephalad  by  tiie  spl^notie 
and  the  prootic  and  ventrallj  bv  the  prootie,  exocdpital,  and  opisthotie. 
At  the  anterior  end  of  the  bone  there  is  a  depression  wfaidi  fmns  the 
posterior  edge  of  the  dilatator  fossa  and  immediately  posterior  and 
slightly  dorsal  to  the  fossa  is  a  facet  for  the  articulation  of  the  posterior 
head  of  the  hyomandibular.  Posterior  to  the  facet  is  a  broad  AaXUxm 
groove,  the  dorsal  edge  forming  the  edge  of  the  groove,  extending  to  tlie 
posterior  end  of  the  bone,  where  it  narrows  as  does  the  bone  itadf. 
Ventro-caudad  to  the  facet  are  two  or  three,  more  or  less  developed 
ridges,  extending  from  the  lower  edge  of  the  facet  to  the  ventro-poste- 
rior  edge  of  the  bone  where  it  unites  by  suture  with  the  opisthotie.  The 
ventral  edge  of  the  bone  curves  sharply  inward,  thus  forming  a  broad 
rounded  ridge  between  the  facet  and  the  point  where  it  unites  with  the 
prootic  and  the  exoccipitaL  The  antero-ventral  edge  of  the  facet  forms 
a  flange-like  shelf  beneath  which  there  is  a  slight  depiesBion  forming, 
together  with  a  flange-like  expansion  of  the  prootie,  a  tooad  gtoofve 
extending  from  that  point  antero-ventrad  on  to  the  piootie.  The  inner 
surface  of  the  pterotic  forms  Hie  dorso-posterior  part  of  the  lakenl  wall 
of  the  brain  case,  there  being  a  large  cavity  passing  latero-eaudad  fron. 
the  main  portion  of  the  brain  case,  and  lying  ventro-mesad  to  the  faeet 
of  the  hyomandibular.  This  cavity  harbors  a  part  of  the  external  soni- 
circular  canal. 

Epiotic. — The  epiotics  (Fig.  1,  epo)  form  a  part  of  the  dorsal 
surface  of  the  cranium.  The  lateral  snrfaee  of  each  forms  the  mnrial 
boundary  of  the  temporal  fossa ;  its  mesial  edge  forms  the  lateral  border 
of  the  supra-temporal  pocket.  The  bone  is  bounded  laterally  by  the 
posterior  process  of  the  parietal  and  pterotic;  ventraUy  and  postero- 
ventrally  by  the  exoccipital  and  mesiaUy  by  the  supra-oeeipitaL  It 
forms  a  tall  ridge  extending  postero-laterad  as  far  caudad  as  the  pterotie 
and  the  opisthotie  above  the  exoccipital,  and  neariy  parallel  to  the 
pterotic.  The  supra-scapular  lies  coi  the  dorsal  surfaces  at  tiie  eandal 
ends  of  the  epiotic  and  pterotic,  thus  forming  a  roof  at  the  posterior 
end  of  the  temporal  fossa.  At  the  anterior  end  the  bones  are  oveilai^ied 
by  the  supra-occipital  and  the  parietals.  The  internal  sur&ee  fomH 
the  dorso-caudal  w^  of  the  brain  case.  These  parts  form  postmociy 
pockets  for  the  posterior  semicircular  canals,  directly  above  and  in 
connection  with  the  exoccipitaL 

Parietal. — The  parietals  (Fig.  1,  p)  form  a  part  of  the 
dorsal  surface  of  the  cranium,  their  lateral  edges  forming  the  mesial 
borders  of  the  temporal  fossa.  Each  is  somewhat  irregular  in  shape 
with  its  broadened  end  cephalad  and  a  long  slender  proeess,  extending 


12  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [182 

caudad  slightly  dorsad  and  laterad  on  the  epiotic  ridge,  which  in  this 
position  projects  over  and  forms  a  part  of  the  roof  of  the  temporal 
fossa.  At  the  posterior  end  of  the  process  there  is  a  foramen,  passing 
cephalad  into  the  bone  for  one  of  the  lateral  line  canals.  The  process 
forms  a  ridge  and  extends  antero-mesad,  uniting  with  a  similar  ridge 
from  the  opposite  side  in  the  median  line.  The  dorsal  surface  of  the 
ridge  is  porous  and  possesses  several  striations  parallel  with  the  ridge. 
At  the  anterior  end  the  bone  joins  by  suture  with  the  frontal;  it  is 
supported  laterally  by  the  pterotic  and  mesially  and  ventrally  by  the 
epiotic  and  supra-occipital.  In  the  suture  between  the  parietal  and 
supra-occipital  on  each  side  of  the  median  line  is  a  foramen  for  the 
ramus  lateralis  accessorius  vessels.  The  inner  surface  of  the  bone  lies 
largely  on  the  dorsal  surface  of  the  supra-occipital,  but  lateral  to  the 
plate-like  supra-occipital,  which  covers  the  greater  part  of  the  cranial 
cavity;  the  parietal  forms  a  part  of  the  dorsal  surface  of  the  cavity 
where  it  arches  over  the  space  between  supra-occipital  and  pterotic. 

Opisthotic. — The  opisthotic  (Fig.  6,  opo)  is  a  small  plate-like 
bone,  oval  in  outline,  lying  between  the  pterotic  and  the  exoccipital. 
The  antero-dorsal  edge  overlaps  the  postero-ventral  edge  of  the  pterotic 
and  the  ventral  edge  overlaps  the  exoccipital,  thus  forming  the  latero- 
caudal  edge  of  the  skull.  It  is  drawn  out  caudad  into  a  rounded  process 
which  projects  beyond  the  exoccipital  and  even  with  the  pterotic.  The 
opisthotic  forms  the  posterior  lateral  wall  of  the  temporal  fossa,  from 
the  point  of  its  union  with  the  pterotic  on  the  mesial  surface.  The 
posterior  end  of  the  bone  has  a  bulb-like  appearance  and  is  united  by  a 
cartilaginous  ligament  to  the  suprascapular. 

Exoccipital. — The  exoccipitals  (Figs.  1,  6,  8,  eo)  are  irregu- 
lar bones  which  form  a  part  of  the  lateral  and  of  the  posterior  surface 
of  the  cranium  and  of  the  brain  case.  A  well  defined  angle,  ventral  to 
the  opisthotic,  separates  the  lateral  from  the  candal  surfaces.  That 
part  which  forms  the  porterior  portion  lies  directly  below  the 
epiotic  and  a  part  of  it  forms  the  base  of  the  epiotic  ridge.  The  dorsal 
edge  also  borders  on  and  forms  the  posterior  edge  of  the  floor  of  the 
temporal  fossa.  That  part  posterior  to  the  angle  extends  backward 
and  forms  a  rounded  head,  the  occipital  condyle,  which  looks  caudad 
and  slightly  ventrad,  articulating  with  an  anterior  process  of  the  first 
vertebra.  The  two  condyles  are  dorso-laterad  to  the  basioccipital  and 
laterad  to  the  foramen  magnum.  Ventrad  to  the  epiotic  ridge  and  the 
temporal  fossa,  the  bone  extends  caudad  and  mesad,  uniting  in  the 
median  line  with  its  fellow  of  the  opposite  side ;  thus  forming  the  roof 
of  the  medulla  oblongata.  It  is  overlapped  in  the  median  line  by  a 
ventro-posterior  process  of  the  supra-occipital.  Slightly  above  the  angle 
separating  the  posterior  and  lateral  surfaces,  there  is  a  small  depression 


183]  OSTEOLOGY   OF  LORICATI—GUTBERLET  13 

or  groove,  dorso-cephalad  to  the  condyle,  extending  upward  to  the  pos- 
terior end  of  the  temporal  fossa.  The  lateral  surface  of  the  bone  is 
irregular  in  shape  and  possesses  a  broad  deep  groove  extending  from 
slightly  cephalad  of  the  angle  separating  the  lateral  and  posterior  sur- 
faces to  about  the  middle  of  the  prootic.  At  the  posterior  end  of  the 
groove  there  is  the  foramen  for  the  vagus  nerve  and  slightly  anterior 
to  this,  another  foramen  for  the  glossopharyngeus  nerve  perforates  the 
bone  in  the  same  groove.  On  the  posterior,  dorsal  surface,  anterior  to 
the  condyle,  are  two  foramina  for  the  passage  of  the  occipital  nerves. 
The  internal  surface  forms  part  of  the  posterior  and  part  of  the  lateral 
walls  of  the  brain  case  and  the  dorsal  wall  of  the  medulla  oblongata. 
The  ventro-mesial  edge,  overlapping  the  basioccipital,  forms  a  lateral 
recess  with  the  groove  of  the  basioccipital  on  each  side  of  the  cavum 
sinus  imparis.  Dorsal  to  this  recess,  a  larger  cavity  which  lies  slightly 
dorso-cephalad  to  the  vagus  foramen,  lodges  the  ampulla  of  the  pos- 
terior semicircular  canal.  The  exoccipital  unites  cephalad  with  the 
prootic,  ventrad  with  the  basioccipital,  dorsad  with  the  opisthotic  and 
epiotic,  and  mesad  with  its  fellow  from  the  opposite  side  and  the  supra- 
occipital. 

Supraoccipital. — The  supraoccipital  (Figs.  1,  8,  so)  forms  the 
dorso-posterior  portion  of  the  skull,  lying  between  the  epiotics,  with 
a  process  between  the  exoccipitals,  and  also  beneath  the  parietals  and 
the  posterior  part  of  the  frontals,  thus  forming  the  roof  of  the  brain 
case  as  well  as  a  part  of  the  posterior  wall.  Between  the  epiotics  it  has 
a  deep  groove,  extending  from  the  dorsal  surface,  postero-ventrad,  al- 
most to  the  foramen  magnum,  where  it  ends  in  a  process  between  the 
exoccipitals.  The  groove,  the  supra-temporal  pocket,  is  formed  by  a 
process  on  either  side  which  overlaps  the  epiotics.  On  the  dorsal  sur- 
face it  has  a  small  longitudinal  crest  in  the  median  line  extending 
cephalad  from  the  anterior  end  of  the  groove  to  the  point  where  the 
bone  is  overlapped  by  the  parietals.  The  inner  surface  forms  the  roof 
of  the  brain  case  as  it  has  developed  into  a  thin  plate-like  bone  beneath 
the  parietals  and  the  posterior  part  of  the  frontals.  It  has  a  smooth 
surface  with  a  ridge  at  the  posterior  end  extending  postero-ventrad 
from  the  dorsal  surface  toward  the  foramen  magnum.  Beneath  the 
point  of  articulation  with  the  parietals  and  frontals  a  small  flange  is 
developed  on  the  ventral  surface  near  the  lateral  margin  which  extends 
latero-cephalad,  and  unites  with  a  similar  flange  from  the  sphenotic  by 
a  cartilaginous  ligament.  In  the  base  of  the  flange  is  a  foramen  for  the 
ramus  lateralis  accessorius  vessel  which  passes  over  the  supra-occipital 
between  it  and  the  parietal. 

Basioccipital. — The  basioccipital  (Figs.  1,  6,  8,  bo)  forms  the. 
ventro-posterior  end  of  the  cranium,  the  posterior  end  of  the  myodome, 


14  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [184 

and  the  posterior  part  of  the  floor  of  the  brain  cavity.  On  its  dorsal 
surface  (floor  of  the  brain  case)  are  two  longitudinal  grooves,  one  on 
each  side  of  the  median  line,  lying  along  the  lateral  walls  of  the  bone 
and  separated  by  a  rounded  ridge  in  the  median  line.  These  grooves 
are  open  throughout  the  anterior  half  but  are  covered  in  the  posterior 
half  by  the  edges  of  the  exoccipitals  which  overlap  into  the  brain  cavity 
and  with  the  groove  form  recesses  on  each  side  as  it  passes  backwards 
on  each  side  of  the  pit  of  the  cavum  sinus  imparls,  reaching  almost  to 
the  conical,  vertebra-like,  depression  on  the  posterior  end.  The  cavum 
sinus  imparis  is  a  deep  pit  on  the  dorsal  surface  in  the  median  line  near 
the  posterior  end,  only  separated  by  a  single  thickness  of  bone  from  the 
conical,  vertebra-like,  depression.  This  pit  lies  on  the  surface  of  the 
median  rounded  ridge  between  the  lateral  grooves  which  form  the  re- 
cesses in  connection  with  the  overlapping  mesial  edges  of  the  exoccipi- 
tals. As  the  cavum  sinus  imparis  passes  backward  it  gradually  becomes 
deeper  until  it  forms  a  saccular  cavity  at  the  posterior  end.  The  ventral 
surface  of  the  bone  possesses  a  long  groove  the  ventro-lateral  edges  of 
which  almost  form  a  circle  in  connection  with  the  parasphenoid.  This 
groove  tapers  gradually  into  a  narrow  tube  which  passes  to  the  posterior 
end  and  opens  to  the  exterior  by  a  slit-like  opening  on  the  ventral  sur- 
face. This  tube  forms  the  posterior  portion  of  the  myodome.  On  the 
lateral  surface  of  the  bone  is  a  rounded  ridge,  arising  at  the  dorso- 
anterior  edge,  where  it  is  a  continuation  of  a  similar  ridge  from  the 
prootic,  and  extending  postero-ventrad  nearly  to  the  ventral  surface  of 
the  bone.  The  posterior  end  is  rounded,  with  a  slight  conical  depression 
which  forms  the  facet  for  the  articulation  with  the  first  vertebra. 

Myodome. — The  myodome  is  a  long  funnel  shaped  cavity,  formed 
by  the  basisphenoid,  the  two  prootics,  the  parasphenoid,  and  the  basi- 
occipital.  The  funnel  is  triangular  in  outline,  located  between  the  two 
prootics  and  ventral  to  the  basisphenoid,  the  pedicle  of  which  bisects 
the  anterior  end  of  the  cavity.  It  becomes  narrow  as  it  extends  caudad 
into  the  basioccipital  where  it  tapers  to  a  tube  and  opens  to  the  exterior 
by  a  slit  on  the  ventral  surface.  There  is  an  oval  opening  between  the 
basisphenoid  and  the  partition  of  the  prootics  for  the  pituitary  body. 
Immediately  posterior  to  this  opening  on  the  dorso-lateral  surface  of 
the  myodome  there  is  a  pocket  which  extends  upward  toward  the 
trigemino-facial  chamber  and  is  only  separated  from  it  by  a  thin  parti- 
tion. Here  the  myodome  is  widest  and  narrows  rapidly  caudad  until  it 
forms  the  tube.  At  the  median  ventral  edges  of  prootics  and  basi- 
occipital is  a  long  slit-like  opening,  the  hypophysial  fenestra,  covered  by 
the  parasphenoid,  except  at  the  posterior  end  where  it  opens  to  the 
exterior.  The  myodome  contains  the  eye  muscles,  which  are  attached 
to  the  walls  and  roof  of  the  cavity  and  pass  cephalad  into  the  orbit. 


185]  OSTEOLOGY   OF  LORICATI —GUTBERLET  IS 

Orbit. — The  orbits  are  formed  by  the  prefrontals,  frontals,  sphe- 
notics,  and  suborbitals.  They  are  large  in  Ophidon  and  the  two  are 
separated  by  the  partial  partition  of  the  orbitosphenoid  which  is  carti- 
laginous at  its  anterior  portion  and  membranous  at  the  posterior.  At 
the  anterior  end  the  partition  comes  in  contact  with  the  prefrontals  in 
the  median  line  and  at  the  posterior  end  it  comes  in  contact  with  the 
dorsal  surface  of  the  basisphenoid  and  the  pedicle  unites  with  the  mem- 
brane at  the  point  of  contact  with  the  parasphenoid.  Dorsal  to  the 
basisphenoid  the  membranous  partition  divides,  extends  laterally  and 
unites  on  each  side  with  the  ventro-mesial  edge  of  the  alisphenoid  and 
the  ventral  processes  of  the  frontal,  thus  forming  the  posterior  wall  of 
the  orbit  and  the  anterior  wall  of  the  brain  cavity.  Directly  dorsal  to 
the  basisphenoid  and  slightly  lateral  to  the  median  line  there  is  an 
opening  through  the  membrane  for  the  passage  of  the  optic  nerve. 
Above  the  openings  for  the  optic  nerves  in  the  median  line  against  the 
dorsal  wall  there  is  an  opening  for  the  olfactory  nerves  which  pass 
cephalad  and  divide,  one  passing  on  either  side  of  the  partition  and 
through  the  foramina  in  the  prefrontal  into  the  nasal  sac. 

Brain  Cavity. — The  brain  cavity  in  Ophidon  is  quite  large 
and  extends  from  the  posterior  end  of  the  orbit,  from  which  it  is  sepa- 
rated by  the  lateral  partitions  of  the  infraorbital  membrane,  to  the  post- 
erior wall  of  the  cranium.  The  cavity  has  a  series  of  recesses  on  the 
dorso-lateral  walls  for  parts  of  the  brain  and  on  the  ventral  surface  there 
is  a  groove  like  cavity,  the  cavum  sinus  imparls,  beneath  the  foramen  mag- 
num. On  the  floor  of  the  brain  case  are  two  grooves  which  extend  caudad 
along  the  lateral  walls  of  the  basioccipital,  parallel  to  the  cavum  sinus 
imparls  to  the  posterior  end.  The  mesial  edges  of  the  exoccipitals  overlap 
and  form  saccular  recesses  of  these  grooves.  Above  each  saccular  recess 
there  is  a  cavity — the  part  of  the  labyrinth  enclosing  that  portion  of 
the  posterior  semicircular  canal  which  is  located  in  the  exoccipital. 
Dorsal  to  this  is  a  large  recess  in  the  epiotic  which  is  for  the  rest  of  the 
posterior  semicircular  canal.  Antero-lateral  to  this  recess  in  the  pterotic 
there  is  a  large  recess  for  the  external  semicircular  canal,  with  two  pits 
in  the  ventral  surface  for  the  ampulla  of  this  canal.  One  of  these  pits 
is  located  in  the  prootic  and  the  other  in  the  pterotic.  Anterior  to  this 
recess  there  is  another  for  the  anterior  semi-circular  canal.  This  one  is 
divided  into  two  parts  by  a  flange-like  partition  which  extends  dorso- 
cephalad  from  the  floor  of  the  cavity.  The  anterior  part  of  the  cavity 
lies  in  the  prootic  and  lodges  the  ampulla,  while  the  posterior  lies  in 
the  sphenotic  and  lodges  the  body  of  the  canal.  Directly  anterior  to  the 
anterior  semicircular  canal  there  is  another  shallow  cavity — the  trige- 
mino-facial  chamber — which  lies  nearly  in  the  line  with  the  pituitary 
opening  between  the  basisphenoid  and  the  prootics.    The  dorso-anterior 


16  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [186 

end  of  the  brain  case  is  located  between  the  ventral  flanges  of  the 
frontals. 

Facial  Bones 

PremaxUlary. — The  premaxillary  (Fig  9)  is  a  long  curved 
bone  bearing  teeth.  Its  anterior  end  is  thickened  and  bears  two  dorsal 
processes  extending  dorso-caudad,  with  a  V-shaped  slit  between  them. 
The  anterior  process  is  long,  slender,  and  laterally  flattened  at  the  base 
and  gradually  becomes  rounded  distally  until  at  its  end,  where  it  articu- 
lates with  the  ethmoid,  it  is  antero-posteriorly  flattened.  The  posterior 
process  is  broad  and  thick  at  the  base  and  as  it  nears  the  end  it  makes 
a  sharp  curve  and  comes  to  a  point  at  its  anterior  edge ;  on  its  anterior 
mesial  surface  it  has  a  deep  depression  into  which  an  angular  process 
of  the  maxilla  passes  as  it  articulates  with  that  bone.  It  is  rounded  on 
its  dorso-lateral  surface  except  at  a  point  slightly  posterior  to  the  middle 
where  it  has  broadened  and  flattened  into  a  sharp  edge ;  from  this  point 
it  gradually  tapers  to  a  long  slender  point  which  extends  on  the  lateral 
surface  of  the  mandible.  The  anterior  end  of  the  bone,  anterior  to  the 
processes,  is  rounded  and  thickened  as  it  nears  the  median  line  where 
it  unites  with  its  fellow  from  the  opposite  side.  Two  kinds  of  teeth 
are  present  on  the  premaxillary,  an  inner  row  of  canine-shaped  teeth 
and  from  one  to  several  irregular  rows  of  the  villiform  type. 

Maxillary. — The  maxillary  is  a  long  curved  bone  without  teeth, 
having  a  thick  articular  head  and  a  flat  expanded  hind  end.  The  former 
has  a  large  articular  facet  which  appears  double  on  account  of  a  V 
between  its  articular  surfaces.  The  antero-mesial  of  these  processes 
curves  mesad  and  lies  inside  of  the  dorsal  process  of  the  premaxillary 
with  which  it  articulates,  directly  dorsal  to  the  dorsal  limb  of  the  vomer. 
The  antero-lateral  process  is  drawn  out  into  a  pointed  projection  lateral 
to  the  process  of  the  premaxillary  with  which  the  other  process  articu- 
lates, and  upon  which  the  anterior  ends  of  the  nasal  and  palatine  bones 
rest.  At  the  apex  of  the  V  between  the  articular  processes,  the  bone 
is  rounded  mesad  at  the  point  where  it  fits  over  the  process  of  the  pre- 
maxillary. The  ventral  edge  of  the  first  suborbital  rests  on  the  dorsal 
surface  of  the  maxilla  for  some  distance  back  from  the  anterior  end. 
The  posterior  flattened  and  broadened  end  rests  on  the  lateral  edge  of 
the  mandible  as  it  passes  postero-ventrally  from  the  anterior  end. 

Nasal. — The  nasal  is  a  small  bone  connecting  the  prefrontal, 
ethmoid,  and  the  maxilla  and  forming  the  roof  of  the  nasal  pit.  It  is 
Y-shaped,  with  one  edge  of  the  broad  end  lying  on  a  small  process  on 
the  dorso-anterior  edge  of  the  prefrontal  and  the  other  on  the  antero- 
lateral process  of  the  ethmoid.  The  pedicle  extends  cephalad  and  rests 
upon  the  maxilla,  thus  forming  the  roof  of  the  nasal  pit. 


187]  OSTEOLOGY   OF  LORICATI—GUTBERLET  17' 

Suborbitals. — The  suborbital  bones,  three  in  number,  lie  on 
the  lateral  surface  of  the  skull.  The  anterior  end  of  the  series  is  firmly 
attached  to  the  dorsal  edges  of  the  palatine  and  maxillary,  also  articu- 
lated with  the  prefrontal  at  its  lateral  facet.  At  the  posterior  end  the 
third  bone  is  attached  to  the  preopercular,  thus  forming  a  bridge  from 
the  anterior  to  the  posterior  ends  across  the  cheek;  and  also  the  ventral 
boundary  of  the  orbit.  The  suborbitals  are  plate-like  bones.  The  ante- 
rior bone  is  broad,  somewhat  oval  in  shape,  lying  on  the  surface  of  the 
maxillary  for  some  distance  from  the  anterior  end.  Caudad  it  is  united 
with  the  second  suborbital  bone.  The  second  bone  is  elongate  in  shape 
and  about  one-half  as  broad  as  the  anterior  one.  This  bone  really  forms 
the  ventral  boundary  of  the  orbit.  The  third  bone  is  the  longest  and 
passes  from  the  edge  of  the  orbit  and  is  extended  caudad,  forming  the 
suborbital  stay.  It  is  elongate,  and  is  slightly  broadened  at  the  posterior 
end.  Near  the  anterior  end  of  this  bone  is  a  small  postorbital,  forming 
the  posterior  edge  of  the  orbit  and  extending  to  the  edge  of  the  sphenotic. 
In  younger  specimens  this  is  merely  a  cartilage  but  in  more  mature 
forms  it  becomes  ossified.  This  is  a  small  plate-like  bone  lying  in  the 
dermal  tissue. 

Palatine. — The  palatine  is  an  irregular  bone  composed  of  two 
portions,  a  broad  plate  and  an  anterior  rod.  The  plate  is  posterior  and 
is  somewhat  triangular  with  the  apex  pointing  caudad.  On  the  lateral 
surface  it  is  smooth  except  for  some  small  narrow  ridges  which  extend 
postero-ventrad  from  the  dorso-anterior  end.  There  is  a  large  facet  on 
the  dorsal  edge  for  the  articulation  with  the  prefrontal  and  with  an 
edge  of  the  first  suborbital.  This  facet  has  a  deep  pit  which  extends 
as  a  groove  on  the  dorsal  edge  to  the  posterior  end,  and  serves  for  the 
articulation  of  the  mesapterygoid.  The  mesial  edge  of  the  facet  is  ex- 
tended dorsally  into  a  tall  process  which  becomes  attached  to  the  ventral 
edge  of  the  prefrontal.  The  mesial  surface  of  the  palatine  is  roughened 
by  porous  openings  and  bears  a  deep  groove  bounded  by  the  dorso- 
mesial  and  the  ventro-mesial  edges  of  the  bone  extending  from  the 
anterior  end  of  the  posterior  portion  to  the  posterior  end  of  the  bone. 
Two  kinds  of  teeth  are  present  on  the  ventral  surface  which  are  like 
those  on  the  vomer  and  premaxillary — an  inner  row  of  large  teeth  of 
the  canine  variety  and  outer  row  of  small  villiform  type,  more  or  less 
irregularly  arranged.  The  anterior  rod-shaped  part  of  the  bone  is 
somewhat  curved  antero-ventro-laterally  from  the  dorsal  edge  of  the 
triangular  portion,  directly  anterior  to  the  articular  facet  of  the  pre- 
frontal and  the  suborbital  bone.  This  rod  is  somewhat  flattened  dorso- 
ventrally  at  the  anterior  end  where  it  articulates  by  a  ligament  with  the 
dorsal  surface  of  the  maxillary  on  the  antero-lateral  process  of  the  head 
of  that  bone. 


18  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [188 

Mesapterygoid. — The  mesapterygoid,  the  ectopterygoid  of  some 
authors,  is  a  long,  slender,  curved  bone  which  unites  the  palatine 
with  the  quadrate.  The  anterior  end  of  the  mesapterygoid  lies  in  the 
groove  on  the  dorsal  edge  of  the  palatine,  from  there  it  passes  caudad 
for  a  distance,  then  it  curves  ventrally  and  articulates  with  the  anterior 
edge  of  the  quadrate.  It  is  flattened  laterally  at  the  posterior  and 
middle  parts  but  at  the  anterior  end  it  is  flattened  dorso-ventrally. 
There  is  a  small  groove  on  the  ventral  edge  where  it  lies  in  a  groove 
on  the  dorsal  edge  of  the  palatine.  On  the  dorsal  edge  of  the  mesaptery- 
goid there  is  a  long  slender  groove  for  a  membranous  bone,  the  en- 
topterygoid,  which  forms  a  part  of  the  ventral  boundary  of  the  orbit. 
At  the  point  where  the  bone  curves  ventrally  there  is  a  plate-like  process 
on  the  dorsal  edge  which  connects  with  the  mesapterygoid  and  the 
entopterygoid.  On  the  posterior  edge  the  bone  possesses  a  slight  groove 
where  it  unites  with  the  quadrate.  The  bone  tapers  to  a  point  at  its 
postero-ventral  end. 

Hyomandibular. — The  hyomandibular  is  shaped  like  an  arrow 
head  with  the  shank  extending  from  the  ventral  edge.  The  anterior 
end  is  drawn  out  into  a  thin,  pointed,  plate-like  process.  Slightly  dorso- 
caudad  to  the  pointed  end  is  a  thickened  part  which  passes  ventro- 
caudad  across  the  middle  of  the  head  and  also  across  the  shank,  thus 
forming  an  irregular  cross  with  the  shank.  At  the  anterior  end  of  the 
bar  forming  the  cross  is  a  facet,  the  anterior  head  of  which  articulates 
with  the  facet  of  the  sphenotic  directly  above  the  prootic  arcade.  On 
the  posterior  end  of  the  cross  bar  there  is  a  facet  for  the  articulation 
with  the  opercular.  The  shank  passes  upward  through  the  body  of  the 
bone  and  forms  a  double  facet,  the  posterior  head  of  which  articulates 
with  the  facet  of  the  pterotic  immediately  posterior  to  the  dilatator 
fossa.  The  dorso-caudad  part  of  the  posterior  head  articulates  with  a 
flange-like  process  dorso-caudad  to  the  facet.  The  long  shank  extends 
ventrally  and  is  united  to  the  symplectic  at  its  ventral  end  by  a  mass 
of  cartilage.  The  metapterygoid  articulates  with  the  anterior  process  of 
the  hyomandibular  which  is  a  thin  membrane  bone  filling  the  space 
between  the  anterior  bar  of  the  cross  and  the  shank.  Likewise  the  spaces 
between  the  other  bars  are  also  filled  with  a  thin  sheet  of  membrane 
bone,  thus  leaving  slight  depressions  between  the  bars.  There  is  a  deep 
pit  on  the  mesial  surface  at  the  angle  between  the  anterior  bar  and  the 
shank,  which  gives  rise  to  two  canals.  One  passes  ventrally  into  the 
bone  and  opens  on  the  lateral  surface  of  the  shank  just  anterior  to  the 
ridge  which  bounds  the  groove  for  the  articulation  of  the  preopercular. 
This  canal  bears  the  truncus  hyoideo-mandibularis  facialis  vessel.  The 
other  cajial  passes  ventrad  and  caudad,  dividing  into  two  parts;  one 
opens  to  the  exterior  at  the  dorsal  edge  of  the  groove  for  the  articulation 


189]  OSTEOLOGY  OF  LORICATI—GUTBERLET  19 

of  the  preopercTilar  and  between  the  opercular  bar  and  the  shank,  the 
other  opens  at  the  hind  edge  of  the  bone,  directly  beneath  the  opercular 
bar.  These  two  canals  transmit  branches  of  the  nerve  of  the  latero- 
sensory  canal  which  lies  in  the  region  of  the  opercular.  Another  small 
foramen,  in  the  dorsal  edge  of  the  groove  for  the  preopercular,  trans- 
mits a  part  of  the  hyoid  nerve  between  the  hyomandibular  and  the 
preopercular. 

Symplectic. — The  symplectic  is  a  small  paddle-shaped  bone  with 
a  broadened  end  and  a  long  slender  process.  It  articulates  at  its  dorsal 
and  broadened  end  with  the  shank  of  the  hyomandibular  by  a  long  car- 
tilaginous ligament.  The  bone  for  the  most  part  lies  in  a  triangular 
groove  on  the  lateral  surface  of  the  quadrate  with  its  long  process  pene- 
trating the  bone  almost  to  its  articulating  facet  for  the  mandible. 

Metapterygoid. — The  metapterygoid  is  a  broad  plate-like  bone, 
more  or  less  quadrant  shaped  with  two  plate-like  processes.  The  quad- 
rant-shaped part  is  the  ventral  portion  of  the  bone  with  the  round  edge 
united  by  a  cartilaginous  ligament  with  the  dorsal  edge  of  the  quadrate. 
Two  processes  extend  from  the  dorsal  edge  of  the  quadrant.  One  of 
these  is  somewhat  elongated  and  extends  dorso-cephalad  coming  in  con- 
tact with  the  anterior  process  of  the  hyomandibular.  The  other  extends 
caudad  from  the  dorso-posterior  edge  of  the  quadrant,  and  bears  a  V- 
shaped  slit  for  the  hyoid  artery  on  its  ventral  edge.  The  posterior  edge 
comes  in  contact  with  the  anterior  edge  of  the  shank  of  the  hyomandibu- 
lar. Two  small  flanges,  one  on  either  surface  of  the  anterior  process, 
bound  a  groove  on  the  dorsal  edge  which  extends  nearly  the  entire 
length  of  the  process.  The  groove  is  for  the  union  with  the  hyo- 
mandibular. 

Quadrate. — The  quadrate  is  a  quadrant-shaped  bone  with  the 
ventral  point  thickened  and  formed  into  a  head  for  the  articulation  of 
the  articular.  The  dorsal  or  rounded  edge  is  broken  near  the  posterior 
edge  where  the  bone  forms  a  deep  groove  on  the  inner  surface  for  the 
articulation  of  the  symplectic  where  it  passes  downward  into  the  quad- 
rate. There  is  a  groove  on  the  posterior  edge  extending  almost  the 
length  of  the  bone  for  the  contact  with  the  preopercular.  The  anterior 
edge  is  somewhat  roughened  and  possesses  no  groove  where  it  articulates 
with  the  mesapterygoid.  On  the  dorsal  edge  the  quadrate  unites  by  a 
cartilaginous  ligament  with  the  ventral  edge  of  the  metapterygoid  and 
cephalad  with  the  entopterygoid  and  mesapterygoid,  caudad  it  unites 
with  the  preopercular  and  the  symplectic. 

Preopercular. — The  preopercular  (Fig.  4)  is  a  long,  flat,  curved 
bone  with  three  small  barbs  on  its  posterior  side.  A  lateral  line 
sensory  canal  runs  throughout  its  length,  opening  near  the  edge  of  the 
ventral  barb  and  at  the  dorsal  tip  of  the  bone.    There  are  also  other 


20  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [190 

sensory  canals  in  the  bone  with  openings  at  various  points.  The  outer 
surface  is  smooth  except  that  it  has  a  narrow  ridge  at  its  postero-lateral 
edge  which  is  located  slightly  anterior  to  the  spines.  The  notch  or  pit 
formed  by  the  curve  is  fiUed  with  a  thin  wavy  sheet  of  bone  which 
slightly  overlaps  the  caudal  edge  of  the  shank  of  the  hyomandibular. 
Slightly  dorso-anterior  to  the  ridge  is  a  small  roughened  area  for  the 
articulation  of  the  suborbital  stay. 

Mandible. — The  mandible  is  made  up  of  three  bones,  the  dent- 
ary,  articular  and  the  angular.  A  broad  rounded  ridge  runs  from 
slightly  anterior  to  the  head  of  the  articular  nearly  to  the  anterior  end 
of  the  dentary.  On  the  inner  surface  of  the  dentary  is  a  cavity  within 
the  bone  corresponding  to  the  ridge  on  the  exterior;  the  articular  has 
no  cavity  but  a  groove  which  corresponds  to  the  ridge.  In  the  bone 
beneath  the  ridge  there  is  a  latero-sensory  canal  which  extends  from 
the  anterior  end  of  the  dentary  to  the  posterior  end  of  the  articular. 
The  dentary  is  a  long  bone  with  two  long  processes  at  the  posterior  end, 
forming  a  V-shaped  angle  which  fits  over  the  anterior  process  of  the 
articular  for  its  articulation  with  that  bone.  The  lower  surface  is 
broadened  by  a  mesial  extension  of  a  plate-like  bone  forming  the  ventral 
surface.  Two  kinds  of  teeth  are  present  on  the  dentary,  an  inner  row 
of  the  large  canine  ty^e  and  several  irregular  rows  of  the  villiform 
variety. 

Articular. — The  articular  is  united  to  the  dentary  by  several  bands 
where  it  fits  into  the  V-shaped  angle  for  the  union  of  the  two  bones.  This 
bone  has  a  large  facet  for  articulation  with  the  quadrate.  Here  the  bone 
is  quite  broad  and  gives  off  three  processes.  Slightly  anterior  to  the  facet 
it  gives  off  a  dorsal  anterior  process  which  unites  with  the  dorsal  process 
of  the  dentary  by  a  cartilage.  Immediately  ventrad  to  this,  and  anterior 
to  the  facet,  it  gives  off  a  long  process,  the  anterior  end  of  which  fits 
into  the  V-shaped  angle  of  the  dentary.  On  the  ventro-anterior  edge  it 
gives  off  the  third  process  which  fits  over  the  ventral  process  of  the 
dentary.  There  is  a  groove  on  the  inner  surface  of  the  anterior  and 
ventral  processes  and  a  deep  pit  on  the  antero-ventral  edge  of  the  facet. 
Ventro-posterior  to  the  facet  is  located  the  angular  bone  which  serves 
as  an  attachment  for  some  of  the  mandibular  muscles  to  the  quadrate 
and  also  to  the  intraopercular. 


191]  OSTEOLOGY  OF  LORICATI—GUTBERLET  21 

SCORPIONICHTHYS   MARMORATUS 

The  Cranium 

The  skull  (Figs.  2,  5)  of  Scorpionichthys  differs  from  that  of 
Ophidon  only  in  a  few  points.  The  dorsal  surface  is  somewhat  more 
rounded  and  is  covered  with  a  granulated  network.  The  temporal 
fossae  are  slightly  different  in  shape  and  the  orbits  are  smaller  and 
more  circular  in  outline,  also  the  surface  between  them  is  narrower  and 
concave.  On  the  dorsal  surface  of  the  ethmoid  the  longitudinal  groove, 
present  in  Ophidon,  does  not  occur  and  a  large  erect  process  extending 
antero-laterally  from  the  median  line  takes  the  place  of  the  small 
ethmoid  processes.  There  is  a  broad  flange  on  the  posterior  end  of  the 
skull  extending  mesad  from  the  caudal  end  of  the  epiotic  ridge  toward 
the  median  line,  also  the  supra-occipital  possesses  a  crest  on  the  posterior 
surface  extending  from  the  dorsal  edge  to  the  end  of  the  postero-ventral 
process.  The  anterior  end  of  the  temporal  fossa  is  formed  mainly  by 
the  edges  of  the  granulated  network  of  the  parietals  and  pterotic.  The 
parietal  projects  over  the  fossa  for  a  distance  as  also  does  the  epiotic 
which  goes  to  make  up  a  part  of  the  mesial  edge  of  the  roof.  Most  of 
the  roof  is  formed  by  the  extra-scapular  lying  on  the  dorsal  surfaces 
of  the  epiotic  and  pterotic  across  the  fossa.  In  the  dilatator  fossa  the 
sphenotic  forms  the  greater  part  of  the  roof,  in  contrast  to  the  condition 
in  Ophidon;  also  there  are  no  foramina  in  the  fossa  for  the  passage  of 
the  branches  of  the  otic  vessels. 

The  vomer  (Figs.  2,  5  v)  is  relatively  smaller  than  in  Ophidon  but 
has  the  same  general  shape  except  that  the  lateral  expansions  are  not 
as  long  and  the  dorsal  process  is  shorter.  Only  villiform  teeth  are  pres- 
ent; they  are  numerous  and  irregularly  arranged.  The  dorso-anterior 
surface,  slightly  lateral  to  the  median  line,  possesses  a  small  articular 
facet  for  the  articulation  with  a  similar  facet  on  the  mesial  edge  of  the 
maxilla. 

The  ethmoid  (Figs.  2,  5,  eth)  has  no  depression  on  its  lateral  sur- 
faces for  the  nasal  pit.  A  tall  antero-lateral  process  forms  a  V-shaped 
crest  in  the  median  line,  supporting  the  nasal  bones  which  roof  the  pit. 

The  prefrontals  (Figs.  2,  5,  pfr)  are  relatively  large,  especially 
anteriorly;  they  lack  depressions  for  the  nasal  pits.  A  thin  flange 
extends  ventro-caudad  from  the  ventral  surface  of  the  lateral  edge  of 
the  wing-like  expansions  to  the  mesial  portion  where  it  unites  with  the 
parasphenoid  in  the  median  line.  On  the  lateral  edge  of  the  anterior 
portion,  directly  posterior  to  the  vomer  and  anterior  to  the  wing,  there 
is  a  small  facet  for  the  articulation  with  the  palatine. 


22  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [192 

The  f rentals  (Figs.  2,  5,  fr)  are  somewhat  shorter  than  in  Ophidon 
and  the  surface  between  the  orbits  is  markedly  concave.  The  frontals 
unite  with  the  sphenotics  in  the  usual  position  and  form  a  part  of  the 
orbit.  The  surface  directly  posterior  to  the  orbit  is  somewhat  depressed 
and  forms  a  ridge  on  the  ventral  surface  in  the  posterior  part  of  the 
orbit.  On  the  dorsal  surface  of  the  posterior  portion  of  the  bone  there 
is  a  granulated  network  arranged  more  or  less  in  longitudinal  ridges 
with  an  irregular  groove  in  the  median  line  bounded  by  granulated 
ridges.  The  ventral  surface  is  comparatively  smooth  and  the  part 
within  the  orbit  is  not  porous  as  in  Ophidon.  There  is  a  single  ventral 
flange-like  process  on  each  side  of  the  median  line  forming  a  part  of  the 
anterior  boundary  of  the  brain  case.  At  the  caudal  end  the  flange  is 
thickened  and  unites  with  the  alisphenoid.  A  ridge  extends  from  this 
point  laterad  to  the  edge  of  the  bone  at  the  place  where  it  unites  with 
the  sphenotic,  forming  a  triangular  pit  between  the  ridge  and  the  ante- 
rior edge  of  the  latter  bone.  There  is  also  a  small  depression  anterior 
to  the  ridge  between  it  and  the  flange.  In  some  specimens  the  flange 
comes  in  contact  with  the  dorso-lateral  process  of  the  parasphenoid  on 
the  anterior  edge  of  the  alisphenoid. 

The  ventro-posterior  edge  of  the  sphenotic  (Figs.  2,  5,  spo),  in  con- 
nection with  the  dorsal  edge  of  the  prootic  dorsal  to  the  arcade,  forms 
a  facet  for  the  articulation  with  the  anterior  head  of  the  hyomandibular. 
In  Scorpionichthys  the  prootic  forms  nearly  half  of  the  facet  while  in 
Ophidon  it  forms  only  a  very  minor  part  of  it.  The  sphenotic  forms  the 
greater  part  of  the  roof  of  the  dilatator  fossa,  a  condition  slightly 
different  from  Ophidon  where  the  pterotic  forms  the  roof. 

The  pterotic  (Figs.  2,  5,  pto)  forms  only  a  small  part  of  the  dilita- 
tor  fossa  and  has  a  granulated  surface. 

The  alisphenoid  (Fig.  5  als)  is  not  porous  and  is  not  held  between 
the  two  ventral  processes  of  the  frontal.  It  lacks  a  foramen  for  the 
passage  of  the  cerebral  veia  such  as  Allis  ( '09)  found  in  Scorpaena  and 
others.  It  forms  the  dorsal  edge  of  a  large  foramen  which  is  otherwise 
bounded  by  the  edges  of  the  prootic  and  the  parasphenoid  process. 

The  basisphenoid  and  parasphenoid  (Fig.  5,  ps)  are  the  same  as  in 
Ophidon  except  that  in  the  parasphenoid  there  is  a  small  partition 
between  the  two  dorsal  processes  which  separates  the  anterior  and 
posterior  portions. 

The  prootic  (Figs.  2,  5,  pro)  possesses  a  flattened  process  on  its 
dorsal  edge;  this  lies  directly  ventral  to  the  hyomandibular  facets  and 
causes  the  hyomandibular  to  extend  latereiUy  from  the  skull.  The  ven- 
tral surface  of  this  process  contains  a  rounded  pit  which  extends  dorsad, 
almost  between  the  hyomandibular  facets.  On  the  dorso-anterior  edge, 
immediately  dorsal  to  the  arcade,  the  bone  forms  a  part  of  the  facet 


193]  OSTEOLOGY   OF  LORICATI—GUTBERLET  23 

for  the  anterior  head  of  the  hyomandibular.  In  other  respects  this  bone 
is  like  that  of  Ophidon  except  that  the  foramen  for  the  external  carotid 
artery,  the  jugular  vein,  and  parts  of  the  fifth  and  seventh  nerves  are 
located  in  a  pit  slightly  mesial  to  the  arcade. 

The  epiotic  (Figs.  2,  5,  7,  epo)  is  flattened  on  the  dorsal  surface 
and  extends  caudad  into  a  flattened  process  which  forms  a  part  of  the 
dorsal  surface  of  the  cranium.  On  the  meso-posterior  edge  a  flange- 
like process  from  the  posterior  end  of  the  bone  extends  meso-cephalad 
to  the  median  line  where  it  unites  with  a  similar  process  on  the  supra- 
occipital.  The  lateral  edges  of  the  epiotics  project  slightly  over  the 
fossa  and  form  a  part  of  the  roof. 

The  parietals  (Figs.  2,  5,  p)  have  a  granulated  surface  like  that 
of  the  frontal  and  pterotic.  They  lie  on  the  dorsal  surface  of  the  supra- 
occipital  and  form  only  a  small  part  of  the  roof  of  the  brain  case  at  the 
edges  of  the  supraoccipital.  The  bones  do  not  meet  their  whole  length 
in  the  median  line,  but  leave  the  supraoccipital  exposed. 

The  supraoccipital  (Figs.  2,  7,  so)  has  a  flange-like  process  on  the 
posterior  surface  which  is  a  continuation  of  that  on  the  epiotic.  The 
flanges  of  either  side  fuse  in  the  median  line  where  they  come  in  con- 
tact with  the  crest  which  extends  from  the  dorsal  edge  of  the  bone  to 
the  ventral  edge  of  the  process.  Near  the  dorsal  edge  of  the  skull  it 
forms  a  slight  depression  on  the  caudal  surface  in  connection  with  the 
parietal. 

The  basioccipital  (Figs.  2,  5,  7,  ho)  and  exoccipitals  (Figs.  2,  5,  7, 
eo)  are  as  in  Ophidon,  except  that  in  Scorpionichthys  the  condylar  pro- 
cesses and  the  basioccipital  are  longer. 

Facial  Bones 

The  maxilla  is  shorter  and  more  flattened  throughout  its  entire 
length  than  in  Ophidon.  On  its  ventro-mesial  edge  is  a  small  facet  for 
articulation  with  a  similar  facet  on  the  dorsal  surface  of  the  vomer. 

The  premaxillary  (Fig.  10)  is  much  shorter  than  in  Ophidon  but 
the  dorsal  processes  are  the  same.  Only  villiform  teeth  are  present 
which  are  numerous. 

The  palatine  is  similar  in  all  respects  except  that  the  mesial  pro- 
cess is  larger  than  in  Ophidon,  and  only  villiform  teeth  are  present. 

The  hyomandibular  has  a  large  flange-like  process  on  the  outer 
surface  which  extends  ventro-posteriorly  from  the  dorso-anterior  angle 
formed  by  the  irregular  cross,  to  nearly  the  postero-ventral  edge  of  the 
shank.  The  shank  is  broad  and  flattened  throughout  and  unites  with  the 
preopercular,  symplectic,  and  metapterygoid. 

The  preopercular  (Fig.  3)  bears  two  spines,  one  long  and  pointed 
and  the  other  short  and  somewhat  rounded,  a  condition  not  found  in 


24  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [194 

Ophidon.  The  dorsal  edge  of  the  bone  is  drawn  out  into  a  long  slender 
process  which  lies  on  the  posterior  edge  of  the  shank  of  the  hyomandi- 
bular. 

The  mandible  is  shorter  than  in  Ophidon.  There  is  no  ridge  on  the 
lateral  surface  of  the  dentary  nor  is  there  a  cavity  within  it ;  also  there 
is  no  mesial  process  on  the  ventral  edge.  It  possesses  villi  form  teeth 
but  there  seems  to  be  a  modification  of  the  teeth  in  the  inner  row.  These 
are  longer  than  the  others  and  have  assumed  more  or  less  of  a  canine 
shape,  placing  the  Scorpionichthys  and  Ophidon  closer  together. 


195]  OSTEOLOGY   OF  LORICATI—GUTBERLET  25 

HEXAGRAMMOS    DECAGRAMMUS 
The  Skull 

The  dorsal  surface  is  smooth  and  more  rounded  than  either  Ophidon 
or  Scorpionichthys,  on  account  of  the  lateral  extensions  of  the  pterotic 
and  prootic  which  makes  a  broad  and  flat  rather  than  a  deep  temporal 
fossa.  The  supraoccipital  is  especially  conspicuous  as  it  separates  the 
two  parietals  and  comes  to  a  spine-like  point.  On  each  side  of  the 
median  line  the  parietals  form  narrow  ridges  which  extend  postero- 
laterally  on  the  lateral  edges  of  the  epiotics  and  form  the  mesial  edges 
of  the  roof  of  the  temporal  fossa.  The  dilatator  fossae  are  shallow 
grooves  in  the  sphenotic  and  pterotic  bones.    They  lack  foramina. 

The  vomer  (Figs.  12,  13)  in  this  species  has  a  relatively  longer 
dorsal  process  than  either  Ophidon  or  Scorpionichthys.  There  is  no 
articular  facet  on  the  dorso-anterior  edge  for  the  maxilla.  Only  villi- 
form  teeth  are  present. 

The  ethmoid  (Figs.  12,  13)  is  not  grooved  but  slightly  keeled.  It 
has  no  depressions  for  the  nasal  pits  and  the  antero-lateral  processes  for 
the  support  of  the  nasal  bone  are  similar  to  those  of  Ophidon. 

The  prefrontals  (Figs.  12,  13)  have  no  depressions  on  the  dorso- 
anterior  edge  for  the  nasal  pits  and  have  articular  facets  on  the  antero- 
lateral edges  for  the  palatines  as  in  Scorpionichthys. 

The  frontals  have  a  smooth  dorsal  surface  which  is  slightly  grooved 
between  the  orbits.  It  is  not  porous  on  the  ventral  surface  and  possesses 
a  single  flange  process  as  in  Scorpionichthys,  differing  from  Ophidon 
and  Scorpionichthys  in  not  uniting  with  the  sphenotic  to  form  the  pos- 
terior border  of  the  orbit.  As  in  Scorpionichthys,  the  sphenotic,  in 
connection  with  the  prootic,  forms  the  facet  for  the  anterior  head  of 
the  hyomandibular. 

The  pterotic  is  a  thin  flange-like  bone  extending  postero-ventrally 
from  the  sphenotic,  thus  forming  the  ventro-lateral  boundary  of  the 
temporal  fossa. 

On  the  prootic  there  is  a  lateral  flange-like  process  ventral  to  the 
facets  for  the  hyomandibular;  this  extends  out  laterad  below  the  facet 
for  some  distance,  as  in  Scorpionichthys.  The  prootic  forms  a  large 
part  of  the  anterior  facet  for  the  hyomandibular.  No  special  peculi- 
arities are  shown  in  the  arcade  or  the  location  of  the  foramina. 


26  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [196 

The  parasphenoid  has  no  partition  between  the  lateral  processes  to 
separate  the  anterior  and  posterior  portions  and  differs  from  Ophidon 
in  that  the  ventral  surface  of  the  anterior  portion  bears  a  conspicuous 
ridge. 

The  epiotic  ends  posteriorly  in  two  processes. 

The  condylar  processes  of  the  exoccipitals  are  relatively  longer 
than  in  Ophidon  but  not  as  long  as  in  Scorpionichthys. 

Facial  Bones 

The  premaxillary  is  relatively  shorter  than  in  Scorpionichthys  and 
much  shorter  than  in  Ophidon.  Villiform  teeth  are  present  but  there 
is  a  modifification  of  these  in  the  outer  row,  as  they  are  much  heavier 
and  longer  than  those  of  the  inner  rows. 

The  maxilla  has  a  flange  on  its  dorsal  surface  where  it  comes  in 
contact  with  the  first  suborbital  bone.  Posterior  to  this  flange  the  bone 
is  flattened. 

There  is  a  facet  on  the  anterior  mesial  edge  of  the  palatine  where  it 
comes  in  contact  with  the  ethmoid.  Only  the  villiform  teeth  are  present. 
The  shank  of  the^hyomandibular  forms  nearly  a  rectangular  cross  with 
the  bar  which  bears  the  facets  for  the  anterior  head  and  the  opercular 
bone.  This  causes  the  shank,  which  extends  ventrally  and  slightly  pos- 
teriorly in  Ophidon,  and  directly  ventral  in  Scorpionichthys,  to  extend 
antero-ventrally  in  this  form. 

The  metapterygoid  has  a  short  rounded  anterior  process  and  a 
groove,  formed  by  lateral  and  mesial  flanges,  on  the  posterior  edge  for 
the  shank  of  the  hyomandibular  and  the  hyoid  artery. 

There  are  no  particular  differences  shoAvn  in  the  quadrate  except 
that  it  is  more  anterior  in  this  fish  than  in  the  other  species  described,  a 
condition  brought  about  by  the  position  of  the  hyomandibular  shank. 
The  quadrate  lies  ventral  to  the  anterior  edge  of  the  orbit  while  in 
Ophidon  it  lies  ventral  to  the  posterior  edge  and  in  Scorpionichthys  it  is 
ventral  to  the  central  portion  of  the  orbit. 

The  preopercular  lacks  barbs  and  spines  and  has  no  grooves  nor 
ridges.  It  lies  postero-ventral  on  account  of  the  shank  of  the  hyomandi- 
bular and  the  position  of  the  quadrate.  On  this  account  the  posterior 
end  of  the  suborbital  stay  is  somewhat  lower. 

No  lateral  ridge  is  present  on  the  mandible  and  no  cavity  within  the 
dentary,  nor  is  there  a  mesial  flange  on  the  ventral  edge,  as  in  Ophidon. 
The  dentary  is  relativ^ely  much  shorter  than  in  Ophidon  and  somewhat 
shorter  than  in  Scorpionichthys.  Villiform  teeth  are  present  but  there 
is  a  slight  modification  of  those  of  the  outer  row.  They  are  longer  and 
much  heavier  than  those  of  the  inner  rows. 


197]  OSTEOLOGY  OF  LORICATI  —  GUTBERLET  27 

SUMMAEY 

Since  Ophidon  and  Hexagrammos  belong  to  the  same  family, 
Hexagrammidae,  one  might  expect  something  of  a  similarity  in  their 
osteology  and  also  more  marked  differences  between  Scorpionichthys, 
belonging  to  the  family  Cottidae,  and  Ophidon.  From  a  study  of  these 
forms  I  find  that  there  are  more  differences  between  Ophidon  and 
Hexagrammos  than  between  Ophidon  and  Scorpionichthys. 

Some  of  the  differences  between  Ophidon  and  Hexagrammos  are, — 

1.  The  dorsal  surface  is  more  rounded  in  the  latter. 

2.  The  supraoccipital  possesses  a  conspicuous  spine-like  crest  in  the 
median  line  which  entirely  separate  the  parietals  in  Hexagrammos. 

3.  Foramina  are  present  in  the  dilatator  fossa  in  Ophidon  but 
absent  from  Hexagrammos. 

4.  In  Hexagrammos  there  are  no  nasal  pit  depressions  on  the  eth- 
moid and  prefrontal.  The  ethmoid  is  but  slightly  keeled  and  the  anterior 
portion  of  the  prefrontal  possesses  a  lateral  facet. 

5.  In  Ophidon  the  frontal  is  thick  and  porous,  but  in  Hexagram- 
mos, thin  and  smooth,  with  a  single  flange  and  a  single  groove  on  the 
ventral  surface. 

6.  The  sphenotic  does  not  form  part  of  the  posterior  edge  of  the 
orbit  in  Hexagrammos. 

7.  In  Ophidon  only  a  small  part  of  the  anterior  hyomandibular  facet 
is  formed  by  the  prootic,  while  in  Hexagrammos  this  bone  forms  at  least 
half  of  it.  Also  there  is  a  conspicuous  lateral  prootic  process  below  the 
hyomandibular  facet  in  the  latter  genus. 

8.  In  Ophidon  the  hyomandibular  shank  extends  ventro-caudad 
while  in  Hexagrammos  it  extends  ventro-cephalad,  placing  the  quadrate 
further  cephalad. 

9.  In  Hexagrammos  the  preopercular  spines  and  ridges  found  in 
Ophidon  are  absent,  and  the  bone  itself  occupies  a  more  ventral  position. 

10.  Relatively,  the  mandible  is  twice  as  long  in  Ophidon  as  in  Hex- 
agrammos and  the  dentary  possesses  no  lateral  ridge  or  cavity,  nor  a  me- 
sial flange  on  the  ventral  surface. 

11.  A  marked  difference  is  found  in  the  teeth  in  Ophidon  and 
Hexagrammos.  Both  canine  and  villiform  are  found  in  the  former  but 
only  the  villiform  in  the  latter. 


28  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [198 

Some  of  the  likenesses  between  Ophidon  and  Scorpionichthys  are, — 

1.  Dorsally,  both  skulls  are  flattened  and  have  similar  temporal 
fossae. 

2.  The  sphenotic  and  the  frontal  bones  form  the  posterior  edge  of 
the  orbit, 

3.  The  prootic  arcade  and  the  location  of  the  formina  are  identical 
in  both. 

4.  The  alisphenoid  and  the  parasphenoid  are  alike,  with  the  exception 
of  a  small  partition  between  the  dorso-lateral  processes  of  the  para- 
sphenoid in  Scorpionichthys- 

5.  Except  for  the  longer  premaxillary  in  Ophidon,  the  maxilla  and 
the  premaxillary  are  alike  in  both  species. 

6.  The  pterygoids,  symplectic,  and  quadrate  are  alike  in  every 
respect. 

7.  In  Ophidon,  canine  and  villiform  teeth  are  present  and  only 
villiform  in  Scorpionichthys,  but  in  the  latter  the  inner  row  of  mandibu- 
lar teeth  is  better  developed. 


199]  OSTEOLOGY   OF  LORICATI—GUTBERLET  29 

BIBLIOGRAPHY 

Allen,  Wm.  F. 

1905.    The  Blood  Vascular  System  of  the  Loricati,  the  Mail-Cheeked  Fishes. 

Proc.   Wash.   Acad.    Sci.,   7:27-157. 
Allis,  E.  p.,  Jr. 

1889.    The  Anatomy  and  Development  of  the  Lateral  Line  System  in  Amia 

calva.    Jour.  Morph.,  2:463-568. 
1897.    The  Morphology  of  the  Petrosal  Bone  and  the  Sphenoidal  Region  of 

the  Skull  of  Amia  calva.    Zool.  Bull.,  i  :i-26. 
1897.    Cranial  Muscles  and  Cranial  and  First  Spinal  Nerves  in  Amia  calva. 

Jour.  Morph.,  12:487-808. 
1899.    On  certain  Homologies   of  the   Squamosal,   Intercalar,  Ex-occipitale, 

and  Extrascapular  Bones  of  Amia  calva.    Anat.  Anz.,  16:49-72. 

1907.  The    Cranial    Anatomy    of    the    Mail-Cheeked    Fishes.     (Vorlaufige 
Mitt)     Anat.  Anz.,  30:568-573. 

1909.  The  Cranial  Anatomy  of  the  Mail-Cheeked  Fishes.     Zoologica,   Hft. 
57,  209  p.  8  pi. 

Gill,  Theodore. 

1888.  On  the  Classification  of  the  Mail-Cheeked  Fishes.     Proc.  U.  S.  Nat 
Museum,  11:567-592. 

191 1.    Notes  on  the  Structure  and  Habits  of  Wolf-fishes.     Proc.  U.  S.  Nat 
Museum,  39:157-187. 
Lucas,  Frederic  A. 

1904.    The  Osteology  and  Immediate  Relations  of  the  Tile  Fish,  Lepholotilus 
chamaeleonticeps.     Bull.  U.  S.  Bur.  Fish.,  24:81-86, 
McMurrich,  J.  Playfair. 

1884.  The  Osteology  of  Ameiurus  catus.     Proc.  Can.  Inst,  2:270-310. 
Parker,  W.  K. 

1873.    On    the    Structure   and    Development   of   the   Skull   in   the    Salmon. 
(Salmo  salar  L.).    Bakerian  Lecture  II.    Philos.  Trans.  Roy.  Sec.  London, 
163  :95-i45. 
1882.    On  the  Development  of  the  Skull  in  Lepidosteus  osseus.    Phil.  Trans. 
Roy.  Soc.  London,  173 :443-492. 
Stark  s,  E.  S. 

1889.  The  Osteology  and  Relationship  of  the  Percoidean  Fish,  Dinolestes 
Lewini.    Proc.  U.  S.  Nat  Museum,  22:113-120. 

1899.    The  Osteological  Characters  of  the  Fishes  of  the  Suborder  Percesoces. 

Proc.  U.  S.  Nat  Museum,  22:1-10. 
1901.    Synonymy  of  the  Fish  Skeleton.    Proc.  Wash.  Acad.  Sci.,  3:507-539. 

1908.  The  Characters  of  Atelaxis,  a  new^  Suborder  of  Fishes.     Bull.  Mus. 
Comp.  Zool.,  52:16-24. 

1910.  The  Osteology  and  mutual  Relationships  of  the  Fishes  belonging  to 
the  Family  Scombridae.     Jour  Morph.,  21 :77-ioo. 

Wright,  Ramsay. 

1885.  On  the  Skull  and  Auditory  Organ  of  the   Siluroid  Hypophthalmus. 
Trans.  Roy,  Soc.  Canada  (sec.  4),  3:107-118. 


30 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


[200 


EXPLANATION  OF  PLATES 


Abbreviationj 

i 

als 

Alisphenoid 

pfo 

Postfrontal 

ho 

Basioccipital 

Pfr 

Prefrontal 

bs 

Basisphenoid 

pro 

Prootic 

eo 

Elx-occipital 

ps 

Parasphenoid 

epo 

Epiotic 

pto 

Pterotic 

eth 

Ethmoid 

so 

'S'upra-ocdpital 

fr 

Frontal 

spo 

Sphenotic 

opo 

Opisthotic 

tf 

Temporal  fossa 

P 

Parietal 

All  figrures  are  reproduced  from  original  drawings  made  bj'  the  author  from 
preparations. 


201]  OSTEOLOGY  OF  LORICATI—GUTBERLET  31 


PLATE  I 


32  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [202 


EXPLANATION  OF  PLATE 
Fig.    I.    Dorsal  view  of  skull  of  Ophidon  elongatus.    Natural  size. 


.i:r<) 


BO     EG 

PLATE   I 


203]  OSTEOLOGY   OF  LORICATI—GUTBERLET  33 


PLATE  II 


34  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [204 


'       EXPLANATION  OF  PLATE 
Fig.    2.    Dorsal  view  of  skull  of  Scorpionichthys  tnarmoratus.    Natural  size. 


PLATE  II 


205]  OSTEOLOGY  OF  LORICATI—GUTBERLET  35 


PLATE  III 


36  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [206 


EXPLANATION  OF  PLATE 

I 
Fig.    3.     Prepoercul^r  of  Scorpianichthys  marmoratus.    Two-thirds  natural  size. 
Fig.    4.     Preopercular  of  Ophidon  elongatus.    Two-thirdds  natural  size. 
Fig.    5.    Lateral  view  of  skull  of  Scorpianichthys  marmoratus.    Two-thirds  natural 

size. 
Fig.    6.    Lattral  view  of  skull  of  Ophidon  elongatus.    Two-thirds  natural  size. 


SPO 


AL'S  BS   PS 


V  ETII 


OPO 


EO. 


fe"^^  spof^ppop  PTp-rEPO  rm 


PLATE  III 


207]  OSTEOLOGY  OF  LORICATI—GUTBERLET  37 


PLATE  IV 


28  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [208 


EXPLANATION  OF  PLATE 

Fig.    7.     Posterior  view  of  skull  of  Scorpionichthys  marmoratus.     Three-fourths 

natural'  size. 
Fig.    8.     Posterior  view  of  skull  of  Ophidon  elongatus.    Three-fourths  natural  size. 
Fig.    9.    Premaxillary  of  Ophidon  elongatus.    Three-fourths  natural  size. 
Fig.  10.     Premaxillary  of  Scorpionichthys  marmoratus.    Three-fourths  natural  size. 


PLATE  IV 


209]  OSTEOLOGY  OF  LORICATI —GUTBERLET  39 


PLATE  V 


40  ILLINOIS  BIOLOGICAL  MONOGRAPHS  '     [210 


EXPLANATION  OF  PLATE 


HEXAGRAMMOS    DECAGRAMMUS 


Fig.  II.     Posterior  view  of  skull.    One  and  one-half  times  natural  size. 
Fig.  12.    Lateral  view  of  skull.     One  and  one-half  times  natural  size. 
Fig.  13.    Dorsal  view  of  skull.     One  and  one-half  times  natural  size. 


PLATE  V 


I 


.A'fiV 


e 


k 


rrw 


